This invention relates to underwater diving equipment and more particularly to an improved purge valve for use in removing accumulated water from a diver's mask or helmet.
In the use of most diving masks, whether of the partial or full face variety, and of diving helmets, water collects therein in varying amounts due to leakage or to condensation. Masks and helmets have, therefore, often been provided with a purge valve through which such accumulations of water can be periodically discharged from the mask or helmet. The use of such valves is generally in addition to a breathing gas exhaust valve, although in some apparatus the exhaust valve provides a purging function as well.
Prior art purge valves have taken a variety of forms including those having rigid valve members intended to be operated by a pressure differential, yet having a manually operable push buttons or pull knobs, and those having pressure operated rubber flapper valves. The manually operable, spring biased valves have characteristically been difficult to manage with heavily gloved hands and have been subject to entrapment of sand and silt making them difficult to clean, likely to bind or jam, and prone to leakage. The rubber flapper valves are generally subject to leaks and deterioration, are usually incapable of manual operation, and not readily adjustable as to forces necessary to effect opening. The latter renders them generally unsuitable for use in closed or semi-closed breathing circuit diving systems. An example of a known manually or pressure operable purge valve is found at 51 in U.S. Pat. No. 3,968,795, while examples of known flapper type purge valves are shown in U.S. Pat. No. 3,186,005 and U.S. Pat. No. 2,362,240. These known purge valves are representative of valves having the aforementioned disadvantages and shortcomings which are sought to be overcome by the present invention.